As I promised to update on this matter here it comes!!. I had ordered two new hub adjusting nuts because the ones in there looked damaged by being tightened with a punch and hammer and I also ordered a special spanner wrench or ''socket'' to remove and replace those bearing hubs, I then proceeded to torque them to 235 ft pounds then rotate them clock and counter clock wise a few times then back to 95 ft pounds..the issue is still present.
After further investigation I was told that drive unit had been dropped and rebuild twice by the same tech , I was told after rebuild the truck speed was significantly decreased by half. I contacted the tech who performed the job and he sounded like he did not pay attention to detail at the service manual and use the right torque on the job.
My next step is to try to reach those two adjustment cups ( differential and second reduction gear and properly seat them , I think I can get to them without dropping the whole assembly...I will post when this gets done!!
Crownie the truck works in a dry environment and mast and brake switch are ok...no electrical issues or codes...I took out both axles only to find out the adjusting hub nuts are way too loose....looks like..somebody tighten them with a hammer and punch they need about 90 pounds of torque. I order the spanner wrench and new nuts and will update results...wish me luck so I don't have to drop that pumpkin. Thanks for your help greatly appreciatted.
the fc4000 does not use a steer position sensor
the brake pedal switch will reduce speed
the mast staging switch will reduce speed
i suspect your brake switch
if your truck works in water the left front wheel sprays water into the distribution board located under left step
when the board corodes you get many strange faults
try placing blocks under mast so both drive wheels are off of ground, drive unit and observe drive wheels
when releasing accelerator pedal observe if both wheels stop suddenly or if speed winds down